Malignant hyperthermia (MH) is a pharmacogenetic disorder provoked by volatile anesthetics and non-depolarizing muscle relaxants. Its incidence is between 1 in 15,000 and 1 in 50,000 anesthetics with a mortality of approximately 30%. The MH syndrome is characterized by metabolic acidosis, tachycardia, muscle rigidity and markedly elevated temperature. The preoperative diagnosis of MH is difficult because it requires a large muscle biopsy, a laboratory and physiologist dedicated to MH diagnostic studies. Those individuals with a previous family history can be screened for MH by muscle biopsy but the available tests of the muscle also carry a fair degree of uncertainty. This proposal is intended to extend our previous observations that novel low molecular weight proteins are present in MH muscle. We intend to obtain a greater number of muscle specimens from patients who have had verified MH episodes. The muscle proteins will be electrophoresed and the extra proteins isolated and characterized. The extra MH proteins will be quantitated by densitometric scans of the electrophoretic gels and a correlation between MH susceptibility and the amount of extra MH proteins made.